The microsporidian Nosema ceranae was first reported from Beijing, China, in the Asian honey bee, Apis cerana, which is often assumed to be its original host. Nowadays N. ceranae is found worldwide in Apis mellifera and it has been blamed as a cause of colony collapse in A. mellifera. In the centre of Thailand, N. ceranae has been detected in adults of managed A. cerana, wild A. florea and the non-native A. mellifera as well as in wild A. dorsata in the north of Thailand, suggesting that N. ceranae may be widespread and common in honey bees in Thailand and potentially elsewhere in SE Asia.